2-Methyl-2-butene → Ethyl (+/-)-3-[3-carboxy-1-propyl]-5H-dibenzo [a,d]cycloheptene-10-acetate

Participants

Reaction Conditions

Reaction Steps

A solution of ethyl (±)-3-[4-hydroxy-1-butyl]-5H-dibenzo[a,d]cycloheptene-10-acetate (342.4 mg, 0.97 mmole) in anhydrous CH2Cl2 (19 mL) was cooled to 0° C. under argon, and 2,2,6,6-tetramethyloxopiperidinium chloride (J. Org. Chem. 1985, 50, 1332-1334; 260 mg, 1.36 mmole) was added in one portion. The reaction was stirred at 0° C. for 1 hr, then 2-methyl-2-butene (1.2 mL, 11 64 mmole) was added, followed by a cold (0° C.) solution of NaClO2 (0.88 g, 7.76 mmole) and NaH2PO4 (0.90 g, 6.50 mmole) in H2O (26 mL). After 10 min, the reaction was diluted with EtOAc (100 mL) and the layers were separated. The organic layer was washed sequentially with cold 1.0 N HCl (10 mL) and saturated brine (20 mL), dried (MgSO4), and concentrated. Silica gel chromatography (gradient: 1:1 EtOAc/CHCl3 then 9:9:2 EtOAc/CHCl3 /EtOH) gave impure title compound. Rechromatography on silica gel (7:3:0.1 toluene/EtOAc/AcOH) gave the pure title compound (233.7 mg, 66%): TLC (1:1 EtOAc/CHCl3) Rf 0.46; 1H NMR (400 MHz, CDCl3) δ 7.05-7.22 (m, 4 H), 6.92-7.05 (m, 3 H), 4.34 (d, J=15.0 Hz, 1 H), 4.10-4.25 (m, 2 H), 3.80-3.90 (m, 2 H), 3.33 (dd, J=15.1, 4.1 Hz, 1 H), 2.95 (dd, J=15.1, 9.4 Hz, 1 H), 2.48-2.60 (m, 4 H), 2.48-2.60 (m, 4 H), 2.37 (t, J=7.4 Hz, 2 H), 1.87-2.00 (m, 2 H), 1.27 (t, J=7.2 Hz, 3 H); MS (ES) m/e 389 (M+Na)+, 367 (M+H)+.

Provenance & Evidence